Mendoza, armed with an M-16 rifle and small arms, earlier released nine hostages: six Hong Kong nationals and two Filipinos, mainly women and children, police said. He asked for food for those remaining on the bus, which was delivered, and fuel to keep the air-conditioning going.

A handwritten note, signed by Mr Mendoza, saying "BIG DEAL WILL START AFTER 3PM TODAY" was stuck to the door of the bus. A sign stuck to a window said "3PM TODAY DEAD LOCK".

Also stuck to the bus door was a piece of paper with the handwritten message: "BIG MISTAKE TO CORRECT A BIG WRONG DECISION".

A larger piece of paper on the front windshield was headed "RELEASE FINAL DECISION" and then what appeared to be details of his case.

A Philippines police spokesman said the use of force would be a last resort.

Gregorio Mendoza earlier told a local television station that his brother was upset by his treatment and dismissal from the force. "His problem was he was unjustly removed from service. There was no due process, no hearing, no complaint," he said.